When goods and freight are loaded into an enclosure, such as a freight car, van, truck trailer or the like, the enclosure is usually sealed at the point of dispatch by means of a security seal. One type of seal is a metal or plastic wire which passes through the latch to plates on the door. The seal may be provided with a number, time and date of sealing. At the time of delivery, the seal is inspected to see if it is intact.
U.S. Pat. No. 4,118,057 shows a reusable seal consisting of a body and wire loop, the ends of which pass through holes in the body and are clamped in position by plungers actuated by turning a drum rotatively mounted on the body. A pair of visible balls provide a color code which is changed if the drum is rotated to release and unclamp the wire loop providing an indication that the seal has been tampered with.
U.S. Pat. No. 3,779,589 shows a closed loop security seal for detecting unauthorized opening of the closure means of a freight car, meter casing or the like, which embodies a flexible, plastic strap formed at its opposite ends with relatively engageable catch-and-latch portions for locking insertion with a cooperative channel keeper. The strap is formed with tamper-deterring shoulders arranged to cover the ends of the keeper upon locking insertion of the catch-and-latch portions of the strap within the keeper.
While there are various approaches to providing security seals intended to indicated unauthorized opening or tampering of the closure door of a freight car or similar enclosure, these seals generally have disadvantages. While mechanical seals of the type described above can be engaged to appear locked, when, in fact, they are not. Accordingly, it is not uncommon for individuals involved in the loading operation to apply the seals in a manner so that they appear secure when, in fact, they are not engaged. This allows subsequent removal and theft of contents at which time the seal will be engaged so that the container, upon arrival or upon opening, appears to be fully sealed. It is estimated that tremendous losses of stored goods, cargo and freight occur in this manner.
In an effort to provide a higher level of security, various electronic devices have been developed. For example, U.S. Pat. No. 4,766,419 shows an apparatus for recording the opening and closing of a closure member which provides an electrical signal upon opening or closing of the closure member. An electronic circuit generates one of a number of unique codes and stores a generated code. A display device displays a generated code. In one form of the invention, a reusable seal comprises a housing and a cable secured at one end of the housing releasibly attached to the housing at the other end. Operation of a locking mechanism causes an electronic circuit in the housing to generate a random number which is displayed by an LED display. Any change in the number displayed indicates the cable has been released.
U.S. Pat. No. 5,097,253 shows an electronic security device having a communications loop that extends from a control box across the boundary of a portal, such as a door, into a sealed enclosure. The loop must be damaged or moved in order for an entry to be made. The device is adapted to detect unauthorized entries and record the time at which such entry occurs for later reference. The device will also detect attempts to tamper or interfere with operation device and records the time at which such events take place.
Accordingly, a principal object of the present invention is to provide a comparatively inexpensive and easy to use closure seal which will record the time that the seal has been secured so that subsequent inspection can confirm this time. Thus, for example, at the time of dispatch, the seal must be properly engaged in order to cause the time to register. Thus subsequent inspection will indicate whether or not the seal was properly applied at the time of closure, or whether it was left in a condition which would allow subsequent entry.